Method for performing cell reselection and device supporting the same

ABSTRACT

Provided are a method of performing cell reselection and a device supporting the method. According to one embodiment of the present disclosure, the method includes: starting data transmission or data reception while the UE is in radio resource control (RRC) idle state or RRC inactive state; applying an offset value to a serving cell for cell reselection; performing cell reselection based on the applied offset value, during the data transmission or data reception; and stopping applying the offset value to the serving cell, when the data transmission or data reception is succeeded.

This application is a 35 USC § 371 National Stage entry of InternationalApplication No. PCT/KR2019/004088, filed on Apr. 5, 2019, which claimspriority to Korean Patent Application No. 10-2018-0039994, filed on Apr.5, 2018, all of which are incorporated by reference in their entiretyherein.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method for performing cell reselection and adevice supporting the same.

BACKGROUND

Efforts have been made to develop an improved 5th-generation (5G)communication system or a pre-5G communication system in order tosatisfy a growing demand on radio data traffic after commercializationof a 4th-generation (4G) communication system. A standardization act fora 5G mobile communication standard work has been formally started in3GPP, and there is ongoing discussion in a standardization working groupunder a tentative name of a new radio access (NR).

Meanwhile, an upper layer protocol defines a protocol state toconsistently manage an operational state of a user equipment (UE), andindicates a function and procedure of the UE in detail. In thediscussion on the NR standardization, an RRC state is discussed suchthat an RRC_CONNECTED state and an RRC_IDLE state are basically defined,and an RRC_INACTIVE state is additionally introduced.

In NB-IOT or LTE eMTC, UE performing Early Data Transmission maytransmit uplink data or receive downlink data while in RRC_IDLE where UEmay perform cell reselection. In NR, UE may transmit uplink data orreceive downlink data while in RRC_INACTIVE where UE may perform cellreselection.

SUMMARY

According to a prior art, if UE performs data transmission in RRC_IDLEor RRC_INACTIVE while performing cell reselection, UE may re-transmitdata whenever UE changes to another cell according to the cellreselection process. Thus, cell reselection may cause interruption indata transmission by preventing UE from performing data transmission andreception.

According to an embodiment of the present invention, a method performedby a user equipment (UE) in a wireless communication system is provided.The method may comprise: starting data transmission or data receptionwhile the UE is in radio resource control (RRC) idle state or RRCinactive state; applying an offset value to a serving cell for cellreselection; performing cell reselection based on the applied offsetvalue, during the data transmission or data reception; and stoppingapplying the offset value to the serving cell, when the datatransmission or data reception is succeeded.

The method may further comprise: receiving information on the offsetvalue from the network.

The information on the offset value may be received via at least one ofsystem information, RRC message or paging message.

The offset value may be positive value.

The method may further comprise: applying negative value of offset to atleast one of neighbor cell, before performing the cell reselection.

The method may further comprise: considering a frequency of the servingcell as highest priority frequency, before performing the cellreselection.

The method may further comprise: transmitting an indication, whichindicates that serving cell is changed while data transmission or datareception, to a new serving cell when the UE reselects the new servingcell by the cell reselection.

The indication may be transmitted during ran-based notification area(RNA) update procedure.

The indication may be transmitted via a dedicated random access channel(RACH) preamble.

The indication may be transmitted via a media access control (MAC)control element (CE).

According to another embodiment of the present invention, a userequipment (UE) in a wireless communication system is provided. The UEmay comprise: a transceiver for transmitting or receiving a radiosignal; and a processor coupled to the transceiver, the processorconfigured to: start data transmission or data reception while the UE isin radio resource control (RRC) idle state or RRC inactive state; applyan offset value to a serving cell for cell reselection; perform cellreselection based on the applied offset value, during the datatransmission or data reception; and stop applying the offset value tothe serving cell, when the data transmission or data reception issucceeded.

The processor may be further configured to: control the transceiver toreceive information on the offset value from the network.

The information on the offset value may be received via at least one ofsystem information, RRC message or paging message.

The offset value may be positive value.

According to another embodiment of the present invention, a processorfor a wireless communication device in a wireless communication systemis provided. The processor may be configured to control the wirelesscommunication device to: start data transmission or data reception whilethe UE is in radio resource control (RRC) idle state or RRC inactivestate; apply an offset value to a serving cell for cell reselection;perform cell reselection based on the applied offset value, during thedata transmission or data reception; and stop applying the offset valueto the serving cell, when the data transmission or data reception issucceeded.

According to embodiments of the present invention, performing cellreselection to neighbor cell while a UE camping on a serving cell istransmitting or receiving data may be avoided, by applying offset oncells or by adjusting priorities. Even when cell reselection to anothercell is performed, the UE may continue data transmission/reception for anew cell by promptly notifying the cell change.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a wireless communication system to whichtechnical features of the present invention can be applied.

FIG. 2 shows another example of a wireless communication system to whichtechnical features of the present invention can be applied.

FIG. 3 shows a block diagram of a user plane protocol stack to whichtechnical features of the present invention can be applied.

FIG. 4 shows a block diagram of a control plane protocol stack to whichtechnical features of the present invention can be applied.

FIG. 5 shows a method for performing cell reselection according to anembodiment of the present invention.

FIG. 6 shows an example for de-prioritization of cell reselection formobile originating data according to an embodiment of the presentinvention.

FIG. 7 shows an example for de-prioritization of cell reselection formobile terminating data according to an embodiment of the presentinvention.

FIG. 8 shows a method for RAN update during data transmission inRRC_IDLE or RRC_INACTIVE state.

FIG. 9 shows a UE to implement an embodiment of the present invention.

FIG. 10 shows more detailed UE to implement an embodiment of the presentinvention.

DETAILED DESCRIPTION

The technical features described below may be used by a communicationstandard by the 3rd generation partnership project (3GPP)standardization organization, a communication standard by the instituteof electrical and electronics engineers (IEEE), etc. For example, thecommunication standards by the 3GPP standardization organization includelong-term evolution (LTE) and/or evolution of LTE systems. The evolutionof LTE systems includes LTE-advanced (LTE-A), LTE-A Pro, and/or 5G newradio (NR). The communication standard by the IEEE standardizationorganization includes a wireless local area network (WLAN) system suchas IEEE 802.11a/b/g/n/ac/ax. The above system uses various multipleaccess technologies such as orthogonal frequency division multipleaccess (OFDMA) and/or single carrier frequency division multiple access(SC-FDMA) for downlink (DL) and/or uplink (DL). For example, only OFDMAmay be used for DL and only SC-FDMA may be used for UL. Alternatively,OFDMA and SC-FDMA may be used for DL and/or UL.

FIG. 1 shows an example of a wireless communication system to whichtechnical features of the present invention can be applied.Specifically, FIG. 1 shows a system architecture based on anevolved-UMTS terrestrial radio access network (E-UTRAN). Theaforementioned LTE is a part of an evolved-UTMS (e-UMTS) using theE-UTRAN.

Referring to FIG. 1 , the wireless communication system includes one ormore user equipment (UE; 10), an E-UTRAN and an evolved packet core(EPC). The UE 10 refers to a communication equipment carried by a user.The UE 10 may be fixed or mobile. The UE 10 may be referred to asanother terminology, such as a mobile station (MS), a user terminal(UT), a subscriber station (SS), a wireless device, etc.

The E-UTRAN consists of one or more base station (BS) 20. The BS 20provides the E-UTRA user plane and control plane protocol terminationstowards the UE 10. The BS 20 is generally a fixed station thatcommunicates with the UE 10. The BS 20 hosts the functions, such asinter-cell radio resource management (MME), radio bearer (RB) control,connection mobility control, radio admission control, measurementconfiguration/provision, dynamic resource allocation (scheduler), etc.The BS may be referred to as another terminology, such as an evolvedNodeB (eNB), a base transceiver system (BTS), an access point (AP), etc.

A downlink (DL) denotes communication from the BS 20 to the UE 10. Anuplink (UL) denotes communication from the UE 10 to the BS 20. Asidelink (SL) denotes communication between the UEs 10. In the DL, atransmitter may be a part of the BS 20, and a receiver may be a part ofthe UE 10. In the UL, the transmitter may be a part of the UE 10, andthe receiver may be a part of the BS 20. In the SL, the transmitter andreceiver may be a part of the UE 10.

The EPC includes a mobility management entity (MME), a serving gateway(S-GW) and a packet data network (PDN) gateway (P-GW). The MME hosts thefunctions, such as non-access stratum (NAS) security, idle statemobility handling, evolved packet system (EPS) bearer control, etc. TheS-GW hosts the functions, such as mobility anchoring, etc. The S-GW is agateway having an E-UTRAN as an endpoint. For convenience, MME/S-GW 30will be referred to herein simply as a “gateway,” but it is understoodthat this entity includes both the MME and S-GW. The P-GW hosts thefunctions, such as UE Internet protocol (IP) address allocation, packetfiltering, etc. The P-GW is a gateway having a PDN as an endpoint. TheP-GW is connected to an external network.

The UE 10 is connected to the BS 20 by means of the Uu interface. TheUEs 10 are interconnected with each other by means of the PC5 interface.The BSs 20 are interconnected with each other by means of the X2interface. The BSs 20 are also connected by means of the S1 interface tothe EPC, more specifically to the MME by means of the S1-MME interfaceand to the S-GW by means of the S1-U interface. The S1 interfacesupports a many-to-many relation between MMEs/S-GWs and BSs.

FIG. 2 shows another example of a wireless communication system to whichtechnical features of the present invention can be applied.Specifically, FIG. 2 shows a system architecture based on a 5G new radioaccess technology (NR) system. The entity used in the 5G NR system(hereinafter, simply referred to as “NR”) may absorb some or all of thefunctions of the entities introduced in FIG. 1 (e.g. eNB, MME, S-GW).The entity used in the NR system may be identified by the name “NG” fordistinction from the LTE/LTE-A.

Referring to FIG. 2 , the wireless communication system includes one ormore UE 11, a next-generation RAN (NG-RAN) and a 5th generation corenetwork (5GC). The NG-RAN consists of at least one NG-RAN node. TheNG-RAN node is an entity corresponding to the BS 10 shown in FIG. 1 .The NG-RAN node consists of at least one gNB 21 and/or at least oneng-eNB 22. The gNB 21 provides NR user plane and control plane protocolterminations towards the UE 11. The ng-eNB 22 provides E-UTRA user planeand control plane protocol terminations towards the UE 11.

The 5GC includes an access and mobility management function (AMF), auser plane function (UPF) and a session management function (SMF). TheAMF hosts the functions, such as NAS security, idle state mobilityhandling, etc. The AMF is an entity including the functions of theconventional MME. The UPF hosts the functions, such as mobilityanchoring, protocol data unit (PDU) handling. The UPF an entityincluding the functions of the conventional S-GW. The SMF hosts thefunctions, such as UE IP address allocation, PDU session control.

The gNBs and ng-eNBs are interconnected with each other by means of theXn interface. The gNBs and ng-eNBs are also connected by means of the NGinterfaces to the 5GC, more specifically to the AMF by means of the NG-Cinterface and to the UPF by means of the NG-U interface.

A protocol structure between network entities described above isdescribed. On the system of FIG. 1 and/or FIG. 2 , layers of a radiointerface protocol between the UE and the network (e.g. NG-RAN and/orE-UTRAN) may be classified into a first layer (L1), a second layer (L2),and a third layer (L3) based on the lower three layers of the opensystem interconnection (OSI) model that is well-known in thecommunication system.

FIG. 3 shows a block diagram of a user plane protocol stack to whichtechnical features of the present invention can be applied. FIG. 4 showsa block diagram of a control plane protocol stack to which technicalfeatures of the present invention can be applied. The user/control planeprotocol stacks shown in FIG. 3 and FIG. 4 are used in NR. However,user/control plane protocol stacks shown in FIG. 3 and FIG. 0.4 may beused in LTE/LTE-A without loss of generality, by replacing gNB/AMF witheNB/MME.

Referring to FIG. 3 and FIG. 4 , a physical (PHY) layer belonging to L1.The PHY layer offers information transfer services to media accesscontrol (MAC) sublayer and higher layers. The PHY layer offers to theMAC sublayer transport channels. Data between the MAC sublayer and thePHY layer is transferred via the transport channels. Between differentPHY layers, i.e., between a PHY layer of a transmission side and a PHYlayer of a reception side, data is transferred via the physicalchannels.

The MAC sublayer belongs to L2. The main services and functions of theMAC sublayer include mapping between logical channels and transportchannels, multiplexing/de-multiplexing of MAC service data units (SDUs)belonging to one or different logical channels into/from transportblocks (TB) delivered to/from the physical layer on transport channels,scheduling information reporting, error correction through hybridautomatic repeat request (HARQ), priority handling between UEs by meansof dynamic scheduling, priority handling between logical channels of oneUE by means of logical channel prioritization (LCP), etc. The MACsublayer offers to the radio link control (RLC) sublayer logicalchannels.

The RLC sublayer belong to L2. The RLC sublayer supports threetransmission modes, i.e. transparent mode (TM), unacknowledged mode(UM), and acknowledged mode (AM), in order to guarantee various qualityof services (QoS) required by radio bearers. The main services andfunctions of the RLC sublayer depend on the transmission mode. Forexample, the RLC sublayer provides transfer of upper layer PDUs for allthree modes, but provides error correction through ARQ for AM only. InLTE/LTE-A, the RLC sublayer provides concatenation, segmentation andreassembly of RLC SDUs (only for UM and AM data transfer) andre-segmentation of RLC data PDUs (only for AM data transfer). In NR, theRLC sublayer provides segmentation (only for AM and UM) andre-segmentation (only for AM) of RLC SDUs and reassembly of SDU (onlyfor AM and UM). That is, the NR does not support concatenation of RLCSDUs. The RLC sublayer offers to the packet data convergence protocol(PDCP) sublayer RLC channels.

The PDCP sublayer belong to L2. The main services and functions of thePDCP sublayer for the user plane include header compression anddecompression, transfer of user data, duplicate detection, PDCP PDUrouting, retransmission of PDCP SDUs, ciphering and deciphering, etc.The main services and functions of the PDCP sublayer for the controlplane include ciphering and integrity protection, transfer of controlplane data, etc.

The service data adaptation protocol (SDAP) sublayer belong to L2. TheSDAP sublayer is only defined in the user plane. The SDAP sublayer isonly defined for NR. The main services and functions of SDAP include,mapping between a QoS flow and a data radio bearer (DRB), and markingQoS flow ID (QFI) in both DL and UL packets. The SDAP sublayer offers to5GC QoS flows.

A radio resource control (RRC) layer belongs to L3. The RRC layer isonly defined in the control plane. The RRC layer controls radioresources between the UE and the network. To this end, the RRC layerexchanges RRC messages between the UE and the BS. The main services andfunctions of the RRC layer include broadcast of system informationrelated to AS and NAS, paging, establishment, maintenance and release ofan RRC connection between the UE and the network, security functionsincluding key management, establishment, configuration, maintenance andrelease of radio bearers, mobility functions, QoS management functions,UE measurement reporting and control of the reporting, NAS messagetransfer to/from NAS from/to UE.

In other words, the RRC layer controls logical channels, transportchannels, and physical channels in relation to the configuration,reconfiguration, and release of radio bearers. A radio bearer refers toa logical path provided by L1 (PHY layer) and

L2 (MAC/RLC/PDCP/SDAP sublayer) for data transmission between a UE and anetwork. Setting the radio bearer means defining the characteristics ofthe radio protocol layer and the channel for providing a specificservice, and setting each specific parameter and operation method. Radiobearer may be divided into signaling RB (SRB) and data RB (DRB). The SRBis used as a path for transmitting RRC messages in the control plane,and the DRB is used as a path for transmitting user data in the userplane.

An RRC state indicates whether an RRC layer of the UE is logicallyconnected to an RRC layer of the E-UTRAN. In LTE/LTE-A, when the RRCconnection is established between the RRC layer of the UE and the RRClayer of the E-UTRAN, the UE is in the RRC connected state(RRC_CONNECTED). Otherwise, the UE is in the RRC idle state (RRC_IDLE).In NR, the RRC inactive state (RRC_INACTIVE) is additionally introduced.RRC_INACTIVE may be used for various purposes. For example, the massivemachine type communications (MMTC) UEs can be efficiently managed inRRC_INACTIVE. When a specific condition is satisfied, transition is madefrom one of the above three states to the other.

A predetermined operation may be performed according to the RRC state.In RRC_IDLE, public land mobile network (PLMN) selection, broadcast ofsystem information (SI), cell re-selection mobility, core network (CN)paging and discontinuous reception (DRX) configured by NAS may beperformed. The UE shall have been allocated an identifier (ID) whichuniquely identifies the UE in a tracking area. No RRC context stored inthe base station.

In RRC_CONNECTED, the UE has an RRC connection with the network (i.e.E-UTRAN/NG-RAN). Network-CN connection (both C/U-planes) is alsoestablished for UE. The UE AS context is stored in the network and theUE. The RAN knows the cell which the UE belongs to. The network cantransmit and/or receive data to/from UE. Network controlled mobilityincluding measurement is also performed.

Most of operations performed in RRC_IDLE may be performed inRRC_INACTIVE. But, instead of CN paging in RRC_IDLE, RAN paging isperformed in RRC_INACTIVE. In other words, in RRC_IDLE, paging formobile terminated (MT) data is initiated by core network and paging areais managed by core network. In RRC_INACTIVE, paging is initiated byNG-RAN, and RAN-based notification area (RNA) is managed by NG-RAN.Further, instead of DRX for CN paging configured by NAS in RRC_IDLE, DRXfor RAN paging is configured by NG-RAN in RRC_INACTIVE. Meanwhile, inRRC_INACTIVE, 5GC-NG-RAN connection (both C/U-planes) is established forUE, and the UE AS context is stored in NG-RAN and the UE. NG-RAN knowsthe RNA which the UE belongs to.

NAS layer is located at the top of the RRC layer. The NAS controlprotocol performs the functions, such as authentication, mobilitymanagement, security control.

The physical channels may be modulated according to OFDM processing andutilizes time and frequency as radio resources. The physical channelsconsist of a plurality of orthogonal frequency division multiplexing(OFDM) symbols in time domain and a plurality of subcarriers infrequency domain. One subframe consists of a plurality of OFDM symbolsin the time domain. A resource block is a resource allocation unit, andconsists of a plurality of OFDM symbols and a plurality of subcarriers.In addition, each subframe may use specific subcarriers of specific OFDMsymbols (e.g. first OFDM symbol) of the corresponding subframe for aphysical downlink control channel (PDCCH), i.e. L1/L2 control channel. Atransmission time interval (TTI) is a basic unit of time used by ascheduler for resource allocation. The TTI may be defined in units ofone or a plurality of slots, or may be defined in units of mini-slots.

The transport channels are classified according to how and with whatcharacteristics data are transferred over the radio interface. DLtransport channels include a broadcast channel (BCH) used fortransmitting system information, a downlink shared channel (DL-SCH) usedfor transmitting user traffic or control signals, and a paging channel(PCH) used for paging a UE. UL transport channels include an uplinkshared channel (UL-SCH) for transmitting user traffic or control signalsand a random access channel (RACH) normally used for initial access to acell.

Different kinds of data transfer services are offered by MAC sublayer.Each logical channel type is defined by what type of information istransferred. Logical channels are classified into two groups: controlchannels and traffic channels.

Control channels are used for the transfer of control plane informationonly. The control channels include a broadcast control channel (BCCH), apaging control channel (PCCH), a common control channel (CCCH) and adedicated control channel (DCCH). The BCCH is a DL channel forbroadcasting system control information. The PCCH is DL channel thattransfers paging information, system information change notifications.The CCCH is a channel for transmitting control information between UEsand network. This channel is used for UEs having no RRC connection withthe network. The DCCH is a point-to-point bi-directional channel thattransmits dedicated control information between a UE and the network.This channel is used by UEs having an RRC connection.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels include a dedicated traffic channel (DTCH).The DTCH is a point-to-point channel, dedicated to one UE, for thetransfer of user information. The DTCH can exist in both UL and DL.

Regarding mapping between the logical channels and transport channels,in DL, BCCH can be mapped to BCH, BCCH can be mapped to DL-SCH, PCCH canbe mapped to PCH, CCCH can be mapped to DL-SCH, DCCH can be mapped toDL-SCH, and DTCH can be mapped to DL-SCH. In UL, CCCH can be mapped toUL-SCH, DCCH can be mapped to UL-SCH, and DTCH can be mapped to UL-SCH.

Cell reselection criteria is described.

For NB-IoT inter-frequency cell reselection shall be based on ranking.

If threshServingLowQ is provided in SystemInformationBlockType3 and morethan 1 second has elapsed since the UE camped on the current servingcell, cell reselection to a cell on a higher priority E-UTRAN frequencyor inter-RAT frequency than the serving frequency shall be performed if:

-   -   A cell of a higher priority EUTRAN or UTRAN FDD RAT/frequency        fulfils Squal >ThreshX, HighQ during a time interval        TreselectionRAT; or    -   A cell of a higher priority UTRAN TDD, GERAN or CDMA2000        RAT/frequency fulfils Srxlev>ThreshX, HighP during a time        interval TreselectionRAT.

Otherwise, cell reselection to a cell on a higher priority E-UTRANfrequency or inter-RAT frequency than the serving frequency shall beperformed if:

-   -   A cell of a higher priority RAT/frequency fulfils        Srxlev>ThreshX, HighP during a time interval TreselectionRAT;        and    -   More than 1 second has elapsed since the UE camped on the        current serving cell.

Cell reselection to a cell on an equal priority E-UTRAN frequency shallbe based on ranking for Intra-frequency cell reselection.

If threshServingLowQ is provided in SystemInformationBlockType3 and morethan 1 second has elapsed since the UE camped on the current servingcell, cell reselection to a cell on a lower priority E-UTRAN frequencyor inter-RAT frequency than the serving frequency shall be performed if:

-   -   The serving cell fulfils Squal<ThreshServing, LowQ and a cell of        a lower priority EUTRAN or UTRAN FDD RAT/frequency fulfils        Squal>ThreshX, LowQ during a time interval TreselectionRAT; or    -   The serving cell fulfils Squal<ThreshServing, LowQ and a cell of        a lower priority UTRAN TDD, GERAN or CDMA2000 RAT/frequency        fulfils Srxlev>ThreshX, LowP during a time interval        TreselectionRAT.

Otherwise, cell reselection to a cell on a lower priority E-UTRANfrequency or inter-RAT frequency than the serving frequency shall beperformed if:

-   -   The serving cell fulfils Srxlev<ThreshServing, LowP and a cell        of a lower priority RAT/frequency fulfils Srxlev>ThreshX, LowP        during a time interval TreselectionRAT; and    -   More than 1 second has elapsed since the UE camped on the        current serving cell.

Cell reselection to a higher priority RAT/frequency shall takeprecedence over a lower priority RAT/frequency, if multiple cells ofdifferent priorities fulfil the cell reselection criteria.

The UE shall not perform cell reselection to UTRAN FDD cells for whichthe cell selection criterion S is not fulfilled.

For cdma2000 RATs, Srxlev is equal to −FLOOR(−2×10×log 10 Ec/Io) inunits of 0.5 dB, with Ec/Io referring to the value measured from theevaluated cell.

For cdma2000 RATs, ThreshX, HighP and ThreshX, LowP are equal to −1times the values signalled for the corresponding parameters in thesystem information.

In all the above criteria the value of TreselectionRAT is scaled whenthe UE is in the medium or high mobility state. If more than one cellmeets the above criteria, the UE shall reselect a cell as follows:

-   -   If the highest-priority frequency is an E-UTRAN frequency, a        cell ranked as the best cell among the cells on the highest        priority frequency(ies) meeting the criteria according to        section 5.2.4.6;    -   If the highest-priority frequency is from another RAT, a cell        ranked as the best cell among the cells on the highest priority        frequency(ies) meeting the criteria of that RAT.

Cell reselection to another RAT, for which Squal based cell reselectionparameters are broadcast in system information, shall be performed basedon the Squal criteria if the UE supports Squal (RSRQ) based cellreselection to E-UTRAN from all the other RATs provided by systeminformation which UE supports. Otherwise, cell reselection to anotherRAT shall be performed based on Srxlev criteria.

The cell-ranking criterion Rs for serving cell and Rn for neighbouringcells is defined by Table 1.

TABLE 1 R_(s) = Q_(meas, s) + Q_(Hyst) − Qoffset_(temp) R_(n) =Q_(meas, n) − Qoffset − Qoffset_(temp)

where,

-   -   Qmeas: RSRP measurement quantity used in cell reselections.    -   Qoffset: For intra-frequency: Equals to Qoffsets,n, if        Qoffsets,n is valid, otherwise this equals to zero. For        inter-frequency: Except for NB-IoT, equals to Qoffsets,n plus        Qoffsetfrequency, if Qoffsets,n is valid, plus QoffsetSCPTM, if        QoffsetSCPTM is valid, otherwise this equals to        Qoffsetfrequency. For NB-IoT equals to QoffsetSCPTM, if        QoffsetSCPTM is valid plus QoffsetDedicatedfrequency for any        frequency other than the frequency of the dedicated frequency        offset, if QoffsetDedicatedfrequency is valid, otherwise this        equals to Qoffsetfrequency (if QoffsetDedicatedfrequency is        valid Qoffsetfrequency is not used) plus QoffsetSCPTM, if        QoffsetSCPTM is valid.    -   Qoffset_(temp): Offset temporarily applied to a cell.

If the UE is capable of SC-PTM reception and is receiving or interestedto receive an MBMS service and can only receive this MBMS service whilecamping on a frequency on which it is provided, the UE considersQoffsetSCPTM to be valid during the MBMS sessionas long as the twofollowing conditions are fulfilled:

1) the UE is capable of SC-PTM reception and the reselected cell isbroadcasting SIB20 (or SIB20-NB);

2) Either:

-   -   SIB15 (or SIB15-NB) of the serving cell indicates for that        frequency one or more MBMS SAIs included in the MBMS User        Service Description (USD) of this service; or    -   SIB15 (or SIB15-NB) is not broadcast in the serving cell and        that frequency is included in the USD of this service.

The UE shall perform ranking of all cells that fulfil the cell selectioncriterion S for NB-IoT), but may exclude all CSG cells that are known bythe UE not to be CSG member cells.

The cells shall be ranked according to the R criteria specified above,deriving Qmeas,n and Qmeas,s and calculating the R values using averagedRSRP results.

If a cell is ranked as the best cell the UE shall perform cellreselection to that cell. If this cell is found to be not-suitable, theUE shall not consider this cell and other cells on the same frequency,as candidates for reselection for a maximum of 300s. If the UE entersinto state any cell selection, any limitation shall be removed. If theUE is redirected under E-UTRAN control to a frequency for which thetimer is running, any limitation on that frequency shall be removed.

In all cases, the UE shall reselect the new cell, only if the followingconditions are met:

-   -   the new cell is better ranked than the serving cell during a        time interval TreselectionRAT;    -   more than 1 second has elapsed since the UE camped on the        current serving cell.

In NB-IOT or LTE eMTC, UE performing Early Data Transmission maytransmit uplink data or receive downlink data while in RRC_IDLE where UEmay perform cell reselection. In NR, UE may transmit uplink data orreceive downlink data while in RRC_INACTIVE where UE may perform cellreselection.

If UE performs data transmission in RRC_IDLE or RRC_INACTIVE whileperforming cell reselection, UE may re-transmit data whenever UE changesto another cell according to the cell reselection process. Thus, cellreselection may cause interruption in data transmission by preventing UEfrom performing data transmission and reception.

FIG. 5 shows a method for performing cell reselection according to anembodiment of the present invention.

In step S502, the UE may start data transmission or data reception whilethe UE is in radio resource control (RRC) idle state or RRC inactivestate.

In step S504, the UE may apply an offset value to a serving cell forcell reselection. In prior, the UE may receive information on the offsetvalue from the network. The information on the offset value may bereceived via at least one of system information, RRC message or pagingmessage. The offset value may be positive value. The UE may applynegative value of offset to at least one of neighbor cell, beforeperforming the cell reselection. Further, the UE may consider afrequency of the serving cell as highest priority frequency, beforeperforming the cell reselection.

In step S506, the UE may perform cell reselection based on the appliedoffset value, during the data transmission or data reception. The UE maytransmit an indication, which indicates that serving cell is changedwhile data transmission or data reception, to a new serving cell whenthe UE reselects the new serving cell by the cell reselection. Theindication may be transmitted during ran-based notification area (RNA)update procedure. The indication may be transmitted via a dedicatedrandom access channel (RACH) preamble. The indication may be transmittedvia a media access control (MAC) control element (CE).

In step S508, the UE may stop applying the offset value to the servingcell, when the data transmission or data reception is succeeded.

According to embodiments of the present invention, performing cellreselection to neighbor cell while a UE camping on a serving cell istransmitting or receiving data may be avoided, by applying offset oncells or by adjusting priorities. Even when cell reselection to anothercell is performed, the UE may continue data transmission/reception for anew cell by promptly notifying the cell change.

According to an embodiment of the present invention, cell reselectionduring data transmission in RRC_IDLE or RRC_INACTIVE may bedeprioritized. That is, when a UE is camping a cell and performing datatransmission/reception at the cell, the UE may de-prioritize reselectinganother cell. In this embodiment, three options for de-prioritizing cellreselection may be considered.

-   -   Option 1: The UE may apply an offset to a serving cell or a        neighboring cell in the cell-ranking criterion during data        transmission/reception in RRC_IDLE or RRC_INACTIVE. In this        option, a plus value of offset may be applied to the serving        cell, and a minus value of offset may be applied for the        neighboring cell. Then, when a cell is ranked as the best cell,        the UE may perform cell reselection to that cell. In this        manner, the UE may stay in the original cell.

In an embodiment of the present invention, when UE in RRC_IDLE or RRCINACTIVE initiates uplink transmission (e.g. random access preambletransmission) for sending data to the network or receiving data from thenetwork, or when UE in RRC_IDLE or RRC INACTIVE receives paging forreceiving data from the network, UE may calculate cell-ranking criterionfor a cell by temporarily applying an offset to the cell. The cell maybe one of the serving cell and neighboring cells. Then, when the UEcompletes data transmission or data reception, UE may calculatecell-ranking criterion for a cell by not applying the offset to thecell. The offset may be received from a cell.

-   -   Option 2: The UE may consider the current frequency of the cell        to be the highest priority frequency during data        transmission/reception in RRC_IDLE or RRC_INACTIVE.        Alternatively, the UE may consider frequencies other than the        current frequency of the cell to be the lowest priority        frequency during data transmission/reception in RRC_IDLE or        RRC_INACTIVE.

In an embodiment of the present invention, when UE in RRC_IDLE or RRCINACTIVE camping on a cell initiates uplink transmission (e.g. randomaccess preamble transmission) for sending data to the network orreceiving data from the network, or when UE in RRC_IDLE or RRC INACTIVEreceives paging for receiving data from the network, the UE may considerthe current frequency of the cell to be the highest priority frequency(i.e. higher than any of the network configured values), irrespective ofany other priority value allocated to this frequency. Then, when the UEcamping on a cell completes data transmission or data reception, the UEmay set the current frequency to the priority value that the networkallocated to this frequency.

-   -   Option 3: The UE may apply a first value to Treselection (or        Treselection_none) during no data transmission/reception in        RRC_IDLE or RRC_INACTIVE, while applying a second value to        Treselection (or Treselection_data) during data        transmission/reception in RRC_IDLE or RRC_INACTIVE. Then, the UE        shall reselect the new cell, if the new cell is better ranked        than the serving cell during a time interval Treselection. The        first value is configured by the network and desirably shorter        than the second value. The UE may scale up or down the first        value to calculate the second value.

When UE stops data transmission/reception, the UE may stop applying theabove option. Namely, after UE stops data transmission/reception, the UEmay stop de-prioritizing cell reselection to another cell.

The initiation of uplink transmission may include one of RRC ConnectionRequest message transmission, RRC Connection Resume messagetransmission, RRC Early Data Request message transmission, Random Accesspreamble transmission, and RACH MSG3 transmission.

If UE transmits end of transmission to the network or completes the last(re-) transmission of the last MAC PDU, UE may consider completion ofthe data transmission. If UE receives end of transmission from thenetwork or completes reception of the last MAC PDU, UE may considercompletion of the data reception.

For Option 1, while UE in RRC_IDLE or RRC INACTIVE performs uplinktransmission (e.g. random access preamble transmission) for sending datato the network or receiving data from the network, UE may perform cellreselection by applying offset to the serving cell or the neighbor cell.The cell-ranking criterion Rs for serving cell and Rn for neighboringcells may be defined by Table 2.

TABLE 2 R_(s) = Q_(meas, s) + Q_(Hyst) − Qoffset_(temp) R_(n) =Q_(meas, n) − Qoffset − Qoffset_(temp)

where,

-   -   Qmeas: RSRP measurement quantity used in cell reselections.    -   Qoffset: For intra-frequency: Equals to Qoffsets,n, if        Qoffsets,n is valid, otherwise this equals to zero.

For inter-frequency: Except for NB-IoT, equals to Qoffsets,n plusQoffsetfrequency, if Qoffsets,n is valid, plus QoffsetSCPTM, ifQoffsetSCPTM is valid, otherwise this equals to Qoffsetfrequency.

For NB-IoT equals to QoffsetSCPTM, if QoffsetSCPTM is valid plusQoffsetDedicatedfrequency for any frequency other than the frequency ofthe dedicated frequency offset, if QoffsetDedicatedfrequency is valid,otherwise this equals to Qoffsetfrequency (if QoffsetDedicatedfrequencyis valid Qoffsetfrequency is not used) plus QoffsetSCPTM, ifQoffsetSCPTM is valid plus Qoffset_data if Qoffset data is valid.

-   -   Qoffset_(temp): Offset temporarily applied to a cell.

If UE in RRC_IDLE or RRC INACTIVE camping on a cell initiates uplinktransmission (e.g. random access preamble transmission) for sending datato the network or receiving data from the network, or if UE in RRC_IDLEor RRC INACTIVE receives paging for receiving data from the network, UEmay consider Qoffset data to be valid.

Meanwhile, Qoffset_data may be positive value for serving cell, and maybe negative value for neighbor cells.

The cells shall be ranked according to the R criteria specified above,deriving Qmeas,n and Qmeas,s and calculating the R values using averagedRSRP results.

If a cell is ranked as the best cell the UE shall perform cellreselection to that cell. If this cell is found to be not-suitable, theUE shall not consider this cell and other cells on the same frequency,as candidates for reselection for a maximum of 300s. If the UE entersinto state any cell selection, any limitation shall be removed. If theUE is redirected under E-UTRAN control to a frequency for which thetimer is running, any limitation on that frequency shall be removed.

In all cases, the UE shall reselect the new cell, only if the followingconditions are met:

-   -   the new cell is better ranked than the serving cell during a        time interval Treselection;    -   more than 1 second has elapsed since the UE camped on the        current serving cell.

For Option 3, The UE may apply the first value to Treselection (orTreselection_none) during no data transmission/reception in RRC_IDLE orRRC_INACTIVE, while applying the second value to Treselection (orTreselection_data) during data transmission/reception in RRC_IDLE orRRC_INACTIVE. Then, the UE shall reselect the new cell, if the new cellis better ranked than the serving cell during a time intervalTreselection. The first value may be configured by the network and to beshorter than the second value. The UE may scale up or down the firstvalue to calculate the second value.

The Qoffset_data or the Treselection_data may be transmitted through atleast one of System information (e.g., SystemInformationBlockType2), RRCmessage indicating the state transition to RRC INACTIVE, or RRC IDLE, orsuspend state (e.g., RRCConnectionRelease) or Paging message (e.g., RANpaging or CN paging).

The UE may start or restart de-prioritization of cell reselection toanother cell at the time point when at least one of the followingconditions is met:

-   -   UL data is generated in RRC_INACTIVE or RRC_IDLE and the UE        decides to transmit the data without RRC state transition. If        the UL data is transmitted during RA procedure, the time point        may be defined to the time value of the TTI when the (initial)        preamble is transmitted or when the data with MSG3 is        transmitted. If the UL data is transmitted on the contention        based UL resource or the dedicated UL resource, the time point        may be defined to the time value of the TTI when the initial        data is transmitted.    -   PDCCH used for paging or Paging message for DL data is received        and the paging indicates DL data reception without RRC state        transition. The time point may be defined to the time valued of        the TTI when the paging message is received.    -   A message informing the UE location (RAN/NB level) as an ACK for        paging is transmitted. If the UE informs its location through        the RA procedure, the time point may be defined to the time        value of the TTI when the (initial) preamble is transmitted or        when the MSG3 is transmitted. If CFRA is triggered, it may start        the timer when the dedicated preamble is transmitted. If CBRA is        triggered, it may start the timer when the MSG3 with UEID is        transmitted. If the UE informs its location through the        contention based UL resource, the time point may be defined to        the time value of the TTI when the control message with UEID is        transmitted.

The UE may stop de-prioritization of cell reselection to another cell atthe time point when at least one of the following conditions is met:

-   -   ACK message for UL data is received.    -   ACK message for UL data with end marker is received. If the UL        data is transmitted with RRC message, the time point may be        defined to the time value of the TTI when the RRC response        message is received. Or, if the UL data is transmitted during RA        procedure, the time point may be defined to the time value of        the TTI when the ACK message with MSG4 is received, when the        MSG4 with UEID is received, when the MAC timer for contention        resolution expires, or when the number of preamble transmission        (PREAMBLE_TRANSMISSION_COUNTER) reaches the maximum value.    -   ACK message for DL data is successfully transmitted.    -   ACK message for DL data with end marker is successfully        transmitted. If the UL data is received with RRC message, the        time point may be defined to the time value of the TTI when the        RRC response message is successfully transmitted. Or, if the DL        data is received in the paging message and RA procedure is        performed as the acknowledgement, the time point may be defined        to the time valued of the TTI when the RA procedure is        successfully performed. Or, if the DL data is received during RA        procedure, the time point may be defined to the time value of        the TTI when the ACK for MSG2 (RAR) is successfully transmitted,        or when the ACK for MSG4 (contention resolution) is successfully        transmitted.    -   DL data is successfully received.    -   DL data with end marker is successfully received.

In an embodiment of the present invention, the ACK message may be anacknowledgement in at least one of HARQ, MAC, RRC, or application layer.

FIG. 6 shows an example for de-prioritization of cell reselection formobile originating data according to an embodiment of the presentinvention.

In this embodiment, it may be assumed that the UE in RRC_INACTIVE orRRC_IDLE transmits UL data with MSG3 during RA procedure. In RRC_IDLE,UE may be bandwidth limited and low cost UE (e.g. NB-IOT UE, BL UE) orUE in Enhanced Coverage (e.g. CE mode 1 or 2). The UE may perform EarlyData Transmission. UE may be registered in MME of EPC. In RRC_INACTIVE,UE may be NR UE or eLTE UE. UE may be registered in AMF of 5G Core.

In step S602, UE camping on a cell may receive information onde-prioritization timer from a gNB or eNB. The information onde-prioritization timer may include a value for Qoffset_data or theTreselection_data. The value for Qoffset_data or the Treselection_datamay be received via SIB or RRC messages.

In step S604, if a data is generated in RRC_INACTIVE or RRC_IDLE and theUE decides to transmit the data without RRC state transition (toRRC_CONNECTED), UE may start a de-prioritization timer. While thede-prioritization timer is running, the UE may de-prioritize cellselection to another cell by applying one of the above options possiblywith the received Qoffset_data or the Treselection_data, when theinitial RA preamble or MSG3 is transmitted. The UE may prioritize thecamped cell or the current frequency of the camped cell. Further, inthis step, the UE may transmit random access (RA) preamble.

In step S606, the UE may receive RA response for the RA preamble.

In step S608, the UE may transmit data with MSG 3.

In step S610, the UE may receive the MSG4 with its UEID from thenetwork. When the UE successfully receives MSG 4, the UE may stop thede-prioritization timer. If the UE does not receive MSG 4, the UEtransmit RA preamble to the network until the UE successfully receivesMSG 4 (back to step S604). When the de-prioritization timer expires, theUE may perform the cell reselection.

FIG. 7 shows an example for de-prioritization of cell reselection formobile terminating data according to an embodiment of the presentinvention.

In this embodiment, it may be assumed that the UE in RRC_INACTIVE orRRC_IDLE receives DL data with MSG2 or MSG4 during RA procedure. InRRC_IDLE, UE may be bandwidth limited and low cost UE (e.g. NB-IOT UE,BL UE) or UE in Enhanced Coverage (e.g. CE mode 1 or 2). UE performsEarly Data Transmission. UE may be registered in MME of EPC. InRRC_INACTIVE, UE may be NR UE or eLTE UE. UE may be registered in AMF of5G Core.

In step S702, UE camping on a cell may receive information onde-prioritization timer from a gNB or eNB. The information onde-prioritization timer may include a value for Qoffset_data or theTreselection_data. The value for Qoffset_data or the Treselection_datamay be received via paging message.

In step S704, the UE may transmit RA preamble in response to the pagingmessage.

In step S706, the UE may receive RA response (RAR) from the network.

In step S708, the UE may transmit MSG3 to the network. The MSG3 may beone of RRC Connection Request message transmission, RRC ConnectionResume message transmission, RRC Early Data Request messagetransmission, Random Access preamble transmission, and RACH MSG3transmission.

If the network indicates DL data reception without RRC state transition,the UE may start a de-prioritization timer. In case of contention basedrandom access procedure, the UE may start a de-prioritization timer,when the UE transmits MSG 3 in response to RAR. In case ofnon-contention based random access procedure, the UE may start ade-prioritization timer, when the UE transmits dedicated preambledirectly after receiving paging message. Thus, in case of non-contentionbased random access procedure, step S704 and S706 may be skipped, andthe MSG 3 may be replaced with dedicated preamble.

While the de-prioritization timer is running, the UE may de-prioritizecell selection to another cell by applying one of the above optionspossibly with the received Qoffset_data or the Treselection_data, whenthe RA preamble (e.g. dedicated preamble) is transmitted or the MSG3with UEID is transmitted. The UE may prioritize the camped cell or thecurrent frequency of the camped cell.

In step S710, if the data with its UEID is not successfully receivedfrom the network, the UE may transmit NACK message to the network.

In step S712, if the data with its UEID is successfully received fromthe network, the UE may stop the de-prioritization timer. If thede-prioritization timer expires, the UE may perform the cellreselection.

Even when the UE tries to stay in current serving cell, cell reselectionwould be performed in low probability for some reasons. Hereinafter,procedures performed by the UE after cell reselection to another cell isdescribed.

In this embodiment, while the UE is camping a cell and performing datatransmission/reception in RRC_IDLE or RRC_INACTIVE at the cell, the UEmay reselect another cell due to cell reselection rule. That is, the UEmay move to another cell during performing data transmission/receptionin RRC_IDLE or RRC_INACTIVE state. In this situation, the UE fails tocomplete transmission/reception of data due to the cell reselection.According to an embodiment of the present invention, cell changeindication during data transmission in RRC_IDLE or RRC_INACTIVE state isprovided.

When the UE reselect another cell, the UE may indicate that UE has datato be transmitted or received to the reselected cell. Further, the UEmay indicate cell change to gNB or eNB at the reselected cell.

For an example, the UE may trigger RAN Area Update procedure at thereselected cell. The uplink message of this procedure, e.g. RRCConnection Resume Request message, may indicate one or more of thefollowings:

-   -   MT access, if UE previously performed data reception triggered        by paging    -   MO data, if UE previously performed data transmission    -   Access Category corresponding to the data    -   Failure of data transmission or reception    -   Cell ID corresponding to the previously camped cell where UE        performed data transmission or reception    -   The Sequence Number of the last Layer 2 PDU or SDU that UE        successfully transmitted or received from the previously camped        cell, e.g. The Sequence Number of the last Layer 2 PDU or SDU        positively acknowledged

For another example, the UE may trigger RACH procedure and send a RACHpreamble to gNB or eNB. If configured by gNB or eNB, the RACH preamblemay be dedicated to this purpose. That is, the RACH preamble is specificto indicate the cell change.

For another example, the UE may trigger transmission of a MAC ControlElement and send the MAC Control Element to gNB or eNB at the reselectedcell. The MAC Control Element corresponds to at least one of thefollowings:

-   -   Buffer Status Reporting MAC CE    -   C-RNTI MAC CE    -   Timing Advance Command MAC CE    -   Configured Grant Confirmation MAC CE    -   Power Headroom Report MAC Control Element    -   Data Volume and Power Headroom Report MAC Control Element    -   SPS confirmation MAC Control Element    -   Recommended bit rate MAC Control Element

FIG. 8 shows a method for RAN update during data transmission inRRC_IDLE or RRC_INACTIVE state.

In step S802, UE camping on a cell may receive information onde-prioritization timer from a gNB or eNB. The information onde-prioritization timer may include a value for Qoffset_data or theTreselection_data. The value for Qoffset_data or the Treselection_datamay be received via paging message.

In step S804, the UE may transmit RA preamble in response to the pagingmessage.

In step S806, the UE may receive RA response (RAR) from the network.

In step S808, the UE may transmit MSG3 to the network. The MSG3 may beone of RRC Connection Request message transmission, RRC ConnectionResume message transmission, RRC Early Data Request messagetransmission, Random Access preamble transmission, and RACH MSG3transmission.

In step S810, the cell reselection may be performed. Thus, the UE failsto complete data transmission/reception.

In step S812, the UE may trigger RAN Area Update procedure at thereselected cell. Specifically, the UE may transmit RA preamble tonetwork via the reselected cell (S812 a). The UE may receive RAR inresponse to the RA preamble (S812 b). The UE may transmit RNA updaterequest message to the network via the reselected cell (S812 c).

FIG. 9 shows a UE to implement an embodiment of the present invention.The present invention described above for UE side may be applied to thisembodiment.

A UE 600 includes a processor 610, a memory 620 and a transceiver 630.The processor 610 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 610.

Specifically, the processor 610 is configured to start data transmissionor data reception while the UE is in radio resource control (RRC) idlestate or RRC inactive state.

The processor 610 is configured to apply an offset value to a servingcell for cell reselection. In prior, the processor 610 may receiveinformation on the offset value from the network. The information on theoffset value may be received via at least one of system information, RRCmessage or paging message. The offset value may be positive value. TheUE may apply negative value of offset to at least one of neighbor cell,before performing the cell reselection. Further, the UE may consider afrequency of the serving cell as highest priority frequency, beforeperforming the cell reselection.

The processor 610 is configured to perform cell reselection based on theapplied offset value, during the data transmission or data reception.The processor 610 may transmit an indication, which indicates thatserving cell is changed while data transmission or data reception, to anew serving cell when the UE reselects the new serving cell by the cellreselection. The indication may be transmitted during ran-basednotification area (RNA) update procedure. The indication may betransmitted via a dedicated random access channel (RACH) preamble. Theindication may be transmitted via a media access control (MAC) controlelement (CE).

The processor 610 is configured to stop applying the offset value to theserving cell, when the data transmission or data reception is succeeded.

The memory 620 is operatively coupled with the processor 610 and storesa variety of information to operate the processor 610. The transceiver630 is operatively coupled with the processor 610, and transmits and/orreceives a radio signal.

The processor 610 may include application-specific integrated circuit(ASIC), other chipset, logic circuit and/or data processing device. Thememory 620 may include read-only memory (ROM), random access memory(RAM), flash memory, memory card, storage medium and/or other storagedevice. The transceiver 630 may include baseband circuitry to processradio frequency signals. When the embodiments are implemented insoftware, the techniques described herein can be implemented withmodules (e.g., procedures, functions, and so on) that perform thefunctions described herein. The modules can be stored in the memory 620and executed by the processor 610. The memory 620 can be implementedwithin the processor 610 or external to the processor 610 in which casethose can be communicatively coupled to the processor 610 via variousmeans as is known in the art.

According to embodiment of the present invention shown in FIG. 9 ,performing cell reselection to neighbor cell while a UE camping on aserving cell is transmitting or receiving data may be avoided, byapplying offset on cells or by adjusting priorities. Even when cellreselection to another cell is performed, the UE may continue datatransmission/reception for a new cell by promptly notifying the cellchange.

FIG. 10 shows more detailed UE to implement an embodiment of the presentinvention. The present invention described above for UE side may beapplied to this embodiment.

A UE includes a processor 610, a power management module 611, a battery612, a display 613, a keypad 614, a subscriber identification module(SIM) card 615, a memory 620, a transceiver 630, one or more antennas631, a speaker 640, and a microphone 641.

The processor 610 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 610. Theprocessor 610 may include ASIC, other chipset, logic circuit and/or dataprocessing device. The processor 610 may be an application processor(AP). The processor 610 may include at least one of a digital signalprocessor (DSP), a central processing unit (CPU), a graphics processingunit (GPU), a modem (modulator and demodulator). An example of theprocessor 610 may be found in SNAPDRAGON™ series of processors made byQualcomm®, EXYNOS™ series of processors made by Samsung®, A series ofprocessors made by Apple®, HELIO™ series of processors made byMediaTek®, ATOM™ series of processors made by Intel® or a correspondingnext generation processor.

The processor 610 is configured to start data transmission or datareception while the UE is in radio resource control (RRC) idle state orRRC inactive state.

The processor 610 is configured to apply an offset value to a servingcell for cell reselection. In prior, the processor 610 may receiveinformation on the offset value from the network. The information on theoffset value may be received via at least one of system information, RRCmessage or paging message. The offset value may be positive value. TheUE may apply negative value of offset to at least one of neighbor cell,before performing the cell reselection. Further, the UE may consider afrequency of the serving cell as highest priority frequency, beforeperforming the cell reselection.

The processor 610 is configured to perform cell reselection based on theapplied offset value, during the data transmission or data reception.The processor 610 may transmit an indication, which indicates thatserving cell is changed while data transmission or data reception, to anew serving cell when the UE reselects the new serving cell by the cellreselection. The indication may be transmitted during ran-basednotification area (RNA) update procedure. The indication may betransmitted via a dedicated random access channel (RACH) preamble. Theindication may be transmitted via a media access control (MAC) controlelement (CE).

The processor 610 is configured to stop applying the offset value to theserving cell, when the data transmission or data reception is succeeded.

The power management module 611 manages power for the processor 610and/or the transceiver 630. The battery 612 supplies power to the powermanagement module 611. The display 613 outputs results processed by theprocessor 610. The keypad 614 receives inputs to be used by theprocessor 610. The keypad 614 may be shown on the display 613. The SIMcard 615 is an integrated circuit that is intended to securely store theinternational mobile subscriber identity (IMSI) number and its relatedkey, which are used to identify and authenticate subscribers on mobiletelephony devices (such as mobile phones and computers). It is alsopossible to store contact information on many SIM cards.

The memory 620 is operatively coupled with the processor 610 and storesa variety of information to operate the processor 610. The memory 620may include ROM, RAM, flash memory, memory card, storage medium and/orother storage device. When the embodiments are implemented in software,the techniques described herein can be implemented with modules (e.g.,procedures, functions, and so on) that perform the functions describedherein. The modules can be stored in the memory 620 and executed by theprocessor 610. The memory 620 can be implemented within the processor610 or external to the processor 610 in which case those can becommunicatively coupled to the processor 610 via various means as isknown in the art.

The transceiver 630 is operatively coupled with the processor 610, andtransmits and/or receives a radio signal. The transceiver 630 includes atransmitter and a receiver. The transceiver 630 may include basebandcircuitry to process radio frequency signals. The transceiver 630controls the one or more antennas 631 to transmit and/or receive a radiosignal.

The speaker 640 outputs sound-related results processed by the processor610. The microphone 641 receives sound-related inputs to be used by theprocessor 610.

According to embodiment of the present invention shown in FIG. 10 ,performing cell reselection to neighbor cell while a UE camping on aserving cell is transmitting or receiving data may be avoided, byapplying offset on cells or by adjusting priorities. Even when cellreselection to another cell is performed, the UE may continue datatransmission/reception for a new cell by promptly notifying the cellchange.

In this document, the term “I” and “,” should be interpreted to indicate“and/or.” For instance, the expression “A/B” may mean “A and/or B.”Further, “A, B” may mean “A and/or B.” Further, “A/B/C” may mean “atleast one of A, B, and/or C.” Also, “A, B, C” may mean “at least one ofA, B, and/or C.”

Further, in the document, the term “or” should be interpreted toindicate “and/or.” For instance, the expression “A or B” may comprise 1)only A, 2) only B, and/or 3) both A and B. In other words, the term “or”in this document should be interpreted to indicate “additionally oralternatively.”

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

What has been described above includes examples of the various aspects.It is, of course, not possible to describe every conceivable combinationof components or methodologies for purposes of describing the variousaspects, but one of ordinary skill in the art may recognize that manyfurther combinations and permutations are possible. Accordingly, thesubject specification is intended to embrace all such alternations,modifications and variations that fall within the scope of the appendedclaims.

What is claimed is:
 1. A method performed by a user equipment (UE) in awireless communication system, the method comprising: starting datatransmission or data reception while the UE is in a radio resourcecontrol (RRC) idle state or RRC inactive state; applying an offset valueto a serving cell for cell reselection; performing cell reselectionbased on the applied offset value, during the data transmission or datareception; stopping the application of the offset value to the servingcell based on the data transmission or data reception being successful;and transmitting an indication of a serving cell change, during datatransmission or data reception, to a new serving cell when the UEreselects the new serving cell by the cell reselection.
 2. The method ofclaim 1, further comprising: receiving information on the offset valuefrom a network.
 3. The method of claim 1, wherein the information on theoffset value is received via at least one of system information, a RRCmessage or a paging message.
 4. The method of claim 1, wherein theoffset value is a positive value.
 5. The method of claim 4, furthercomprising: applying a negative offset value to at least one neighborcell, before performing the cell reselection.
 6. The method of claim 1,further comprising: considering a frequency of the serving cell as ahighest priority frequency, before performing the cell reselection. 7.The method of claim 1, wherein the indication is transmitted during aran-based notification area (RNA) update procedure.
 8. The method ofclaim 1, wherein the indication is transmitted via a dedicated randomaccess channel (RACH) preamble.
 9. The method of claim 1, wherein theindication is transmitted via a media access control (MAC) controlelement (CE).
 10. A user equipment (UE) in a wireless communicationsystem, the UE comprising: a transceiver for transmitting or receiving aradio signal; and a processor operatively coupled to the transceiver,the processor configured to: start data transmission or data receptionwhile the UE is in a radio resource control (RRC) idle state or a RRCinactive state; apply an offset value to a serving cell for cellreselection; perform cell reselection based on the applied offset value,during the data transmission or data reception; stop the application ofthe offset value to the serving cell based on the data transmission ordata reception being successful; and control the transceiver to transmitan indication of a serving cell change, during data transmission or datareception, to a new serving cell when the UE reselects the new servingcell by the cell reselection.
 11. The UE of claim 10, wherein theprocessor is further configured to: control the transceiver to receiveinformation on the offset value from a network.
 12. The UE of claim 10,wherein the information on the offset value is received via at least oneof system information, a RRC message or a paging message.
 13. The UE ofclaim 1, wherein the offset value is a positive value.
 14. A processorfor a wireless communication device in a wireless communication system,wherein the processor is configured to control the wirelesscommunication device to: start data transmission or data reception whilethe UE is in a radio resource control (RRC) idle state or a RRC inactivestate; apply an offset value to a serving cell for cell reselection;perform cell reselection based on the applied offset value, during thedata transmission or data reception; stop the application of the offsetvalue to the serving cell based on the data transmission or datareception being successful; and transmit an indication of a serving cellchange, during data transmission or data reception, to a new servingcell when the UE reselects the new serving cell by the cell reselection.15. The method of claim 1, wherein the UE is in communication with atleast one of a mobile device, a network, and/or autonomous vehiclesother than the UE.